This question is testing the understanding of the power sector in India by giving four statements and asking to identify which of those are correct.

Option 1 suggests the installed capacity of power generation in India is around 95,000 MW. This is the correct statement, hence the correct answer.

Option 2 consists of two statements: II- Nuclear plants contribute nearly 15% of total power generation, and III- Hydroelectricity plants contribute nearly 40% of total power generation. Both of these statements are incorrect. The contribution of nuclear power and hydroelectricity to total power generation in India is not as high as mentioned in the statements.

Option 3 also contains two statements: III- Hydroelectricity plants contribute nearly 40% of total power generation, and IV – Thermal plants account for nearly 80% of total power generation. As mentioned earlier statement III is incorrect, and additionally, thermal plants do not account for as high as 80% of total power generation.

Option 4 contains Statement I, which is correct, and Statement IV, which is incorrect. This makes the entire option invalid as it is not wholly correct.

Therefore, option 1 is the correct answer.